The present invention relates to a method for producing a dinuclear transition metal complex as olefin polymerization catalyst. More particularly, the present invention a method for producing a dinuclear transition metal complex of formula (1) by reacting cyclopentadienyl ligand compound of formula (2) and substituted transition metal of formula (3).
Cp-Si(R)2HNANHSi(R)2-Cpxe2x80x83xe2x80x83(Formula 2)
wherein,
A represents C2-30 alkylene, substituted alkylene, arylene, substituted arylene, cycloalkylene, substituted cycloalkylene, biarylene or substituted biarylene;
Cp represents a ligand compound having cyclopentadienyl skeleton selected from the group consisting of cyclopentadienyl, substituted cyclopentadienyl, indenyl, substituted indenyl, fluorenyl and substituted fluorenyl;
R represents C1-20 alkyl or substituted alkyl;
H represents hydrogen atom;
Si represents silicon atom; and
N represents nitrogen atom.
M(NR2xe2x80x2)4xe2x80x83xe2x80x83(Formula 3)
M represents transition metal of Periodic Table IV selected from titanium, zirconium and hafnium;
Rxe2x80x2 represents C1-6 alkyl. 
wherein,
X represents halogen atom or alkylamine; and
A, R, Si, N, Cp and M are same as defined above.
Metallocene catalyst using transition metal of Periodic Table IV has been used as an effective catalyst for various organic catalyst reactions and polymerization reactions for olefin polymer. Further, said metallocene catalyst has many merits of excellent catalytic activity and convenience for controlling molecular weight and molecular weight dispersion compared to conventional Ziegler-Natta catalyst. Among transition metal compounds of Periodic Table IV, the catalyst having cyclopentadienyl skeleton has an excellent catalytic activity and U.S. Pat. Nos. 4,584,346 and 5,965,785 disclosed that constrained geometry catalyst (CGC) having the structure of cyclopentadienyl connected with alkyl or aryl amine shows the excellent catalytic activity.
To obtain said metallocene, following process has been used. (i) Dianion is obtained by reaction of ligand and 2 mole of alkyl lithium using THF or ethyl ether as a solvent; (ii) Ligand of lithium salt is reacted with TiCl4(THF)2, TiCl4(Et2O)2 or ZrCl4 at extremely low temperature (xe2x88x9278xc2x0 C.); (iii) The obtained product is purified and recrystallized after removing by-product, such as, LiCl. However, such process is hard to apply to the industry, because of the using solvent and the extremely low temperature.
Among various metallocene, a dinuclear transition metal complex in which two metals are contained in one compound has been developed. In Korea Polymer Journal, Vol. 9, No.2, pp 71-83(2001), the synthesis of dinuclear transition metal complex and its polymerization method have been disclosed. Such dinuclear transition metal complex has an excellent olefin polymerization activity, especially, the polymerization of ethylene/styrene.
In WO 00/02891, the synthesis of dinuclear transition metal complex having two cyclopentadienyl ligand is disclosed. However, said dinuclear transition metal complex also can be obtained in similar synthetic process of CGC. In detail, (i) Tetra-anion ligand is obtained by reaction of dinuclear ligand and 4 mole of alkyl lithium using THF or ethyl ether as a solvent; (ii) Dinuclear ligand of lithium salt is reacted with 2 mole of TiCl4(THF)2, TiCl4(Et2O)2 or ZrCl4 at extremely low temperature (xe2x88x9278xc2x0 C.); (iii) The obtained product is purified and recrystallized after removing by-product, such as, LiCl. Further, in case of dinuclear metallocene, it is hard to purify or crystallize the metallocene, since two kinds of reaction compound are obtained. Therefore, according to the method in WO 00/02891, dinuclear metallocene is obtained in less than 3% yield, because dinuclear ligand having two cyclopentadienyl is used.
To overcome said drawbacks, the present invention has developed a convenient method for producing dinuclear metallocene in an industrialization scale, which also affords the high yield for preparing dinuclear metallocene by removing the hard steps of metallocene synthesis
The object of the present invention is to provide a method for producing a dinuclear transition metal complex of formula (1) by reacting cyclopentadienyl ligand compound of formula (2) and substituted transition metal of formula (3).
Cp-Si(R)2HNANHSi(R)2-Cpxe2x80x83xe2x80x83(Formula 2)
wherein,
A represents C2-30 alkylene, substituted alkylene, arylene, substituted arylene, cycloalkylene, substituted cycloalkylene, biarylene or substituted biarylene;
Cp represents a ligand compound having cyclopentadienyl skeleton selected from the group consisting of cyclopentadienyl, substituted cyclopentadienyl, indenyl, substituted indenyl, fluorenyl and substituted fluorenyl;
R represents C1-20 alkyl or substituted alkyl;
H represents hydrogen atom;
Si represents silicon atom; and
N represents nitrogen atom.
M(NR2xe2x80x2)4xe2x80x83xe2x80x83(Formula 3)
M represents transition metal of Periodic Table IV selected from titanium, zirconium and hafnium;
Rxe2x80x2 represents C1-6 alkyl. 
wherein,
X represents halogen atom or alkylamine; and
A, R, Si, N, Cp and M are same as defined above.
As a reaction solvent, toluene, xylene or monochlorobenzene can be used.
Further, the reaction is carried out on 20xcx9c120xc2x0 C., preferably, 100xcx9c120xc2x0 C.
Said substituted transition metal is one or more selected from the group consisting of Ti(NR2)4, Zr(NR2)4, Hf(NR2)4 (R is C1-6 alkyl).
In conventional method for producing metallocene compound, tetrahydrofuran (THF) or diethylether (Et2O) has been used as a reaction solvent. Further, the extremely low temperature (xe2x88x9278 xcx9cxe2x88x9240 xc2x0 C.) has to be maintained in order to react the ligand and transition metal. To maintain such extremely low temperature, highly expensive apparatus and cooling agent should be required.
On the other hand, the reactant, tetra-anion ligand has to be made after reacting dinuclear ligand and 4 mole of alkyl lithium in the presence of THF or diethylether for reacting transition metal. However, such tetra-anion ligand is very unstable in the presence of air or moisture as well as the risk of burning. Further, to obtain the dinuclear metallocene, the filtration of LiCl is required. Therefore, the yield of dinuclear metallocene has been very low.
To overcome such drawbacks in conventional method, the present invention has been accomplished.
(1) The present invention has developed the reaction solvent. Therefore, various aromatic solvent can be used in the present invention. As a preferred reaction solvent, toluene or xylene can be used.
(2) Instead of metal compound required for extremely low reaction temperature, such as ZrCl4, HfCl4, TiCl4(THF)2 or TiCl4(Et2O)2, the mild metal compound of Ti(NR2)4, Zr(NR2)4 or Hf(NR2)4 (R is C1-6 alkyl) can be used to proceed with the reaction at higher than room temperature, 20xcx9c120xc2x0 C., preferably, 100xcx9c120xc2x0 C.
(3) Using Ti(NR2)4, Zr(NR2)4 or Hf(NR2)4, tetra-anion ligand unstable to air or moisture is not required as a intermediate. Therefore, it is applied to industrialized scale. Further, without formation of LiCl, unnecessary filtraion process can be reduced.
(4) The reaction between dinuclear ligand and Ti(NR2)4, Zr(NR2)4 or Hf(NR2)4 can be performed in quantitative level. Therefore, the purification and recrystallization to obtain metallocene can be improved and the yield of metallocene also increases.
After Ti(NR2)4, Zr(NR2)4 or Hf(NR2)4 is reacted with the compound of formula (2) purging nitrogen gas, the compound of formula (1) is easily obtained by removing reaction byproduct, dimethylamine. At this time, the obtained compound of formula (1) has C1xcx9c6 alkyl radical as X. Also, the compound of formula (1) has halide as X if trimethyl silylchloride is added.